Automated static perimetry: the influence of myopia and its method of correction

Abstract

Objective To determine how the magnitude of myopia and its method of correction influence visual field testing. Design Prospective observational case series, including comparison of spectacles and contact lenses. Participants One hundred forty-six ophthalmologically normal males 19 to 24 years of age with myopia (spherical equivalent from −0.50 to −14.0 diopters). Methods Participants performed automated static threshold perimetry. Refractive errors were corrected using trial lenses and soft contact lenses. Subjects were tested with both methods of correction, the order of which was randomized. Main outcome measures Threshold sensitivity and global indexes. Results Only one subject (0.7%) had a significant reproducible visual field defect on both methods of correction. Six subjects (4.1%) had a focal visual field defect on one method of correction but not the other. For myopia greater than −4.0 diopters, the mean defect decreased significantly as axial length and degree of myopia increased ( P < 0.01). Similar results were obtained with either method of correction. Conclusions Threshold sensitivity is reduced in moderate and high myopia, regardless of the method of correction. The surprisingly low prevalence of visual field defects in this myopic population disputes the widely held view that myopia is associated commonly with visual field abnormalities. If field defects are found in myopes on automated perimetry, it is advisable to repeat the test with another method of optical correction to check that such defects are genuine and not related to the method of refractive correction.